1. Field of the Invention
This patent pertains to the technological sector of filtration in general, and relates in particular to fluid filtration in the engine field.
2. Description of the Background Art
In both Diesel cycle and Otto cycle internal combustion engines, it is well known that the lubricating oil must be kept filtered.
The problem of effective lubricating oil filtration is not easy to solve, as it involves opposing requirements.
European patent 341349 in the name of the present applicant offers a solution to the problem, consisting of locating within a filter of commonly known type, such as a full-flow filter, three filter cartridges, two of which are connected in series with each other, the combination being connected in parallel with the third.
By carefully coordinating the porosity of the three cartridges, with the parallel cartridge having a porosity between that of the two series-connected cartridges and the most porous cartridge being located externally, the filter of the said patent attains an efficiency not achievable by other full-flow filters, and achievable only by the most costly and complicated known filters such as double filtration filters.
The problem inherent in the various filtration systems will be more apparent on reading said European patent 341349, the entire contents of which is hereby incorporated by reference.
The present patent relates in particular to filters the subject of said European patent.
Although said filters have proved very effective operationally, they present certain constructional difficulties which considerably increase their cost.
In this respect they use three separate filter cartridges of different type, of both paper and unwoven fabric, which not only have to be manufactured separately and then individually mounted in the filter, but require the filter to be provided with an inner metal reinforcement to maintain them in their operating position.